CN112261239B - Plaintext related image encryption method based on PUD adaptive decomposition - Google Patents

Abstract

The invention relates to a plaintext-related image encryption method based on PUD adaptive decomposition. The plaintext image is subjected to adaptive PUD decomposition, and a scrambling-diffusion operation is performed on the decomposed two-dimensional components. The encryption key used in this method is related to the plaintext, and the encrypted image can be effectively resisted against the chosen plaintext attack and the chosen ciphertext attack, and at the same time, it has strong robustness to the filtering noise attack, shearing attack and differential attack, which further improves the The security and robustness of encrypted images can be applied to the fields of image security and image security communication.

Description

A PUD Adaptive Decomposition-Based Plaintext Related Image Encryption Method

technical field

The invention relates to the technical field of image encryption, and more particularly, to a plaintext related image encryption method based on PUD adaptive decomposition.

Background technique

With the rapid development of computer network and communication technology, the use and exchange of multimedia content such as digital images, video sequences and audio signals has shown an explosive growth trend. And digital images as visual multimedia content have been widely used in many fields, including medical, commercial and military. For these applications, the transmission of digital images through public channels and storage on cloud platforms must ensure image security and can only be accessed by authorized agencies. Therefore, the security of digital images becomes more and more important and has become an urgent problem to be solved.

Different from traditional text messages, digital images have the characteristics of large data capacity, strong correlation between adjacent pixels, and high redundancy. Therefore, traditional text encryption algorithms such as AES and DES are no longer suitable for image encryption. At present, image encryption methods can be roughly divided into two types of encryption methods based on spatial domain and based on transform domain. The cryptographic operations commonly used in these two types of cryptographic domains are scrambling-diffusion operations. Since spatial domain-based encryption algorithms usually have a limited key space and are insecure against classical statistical attacks, the spatial domain-based encryption algorithms cannot meet the security requirements. To overcome these limitations, better security is achieved using permutation diffusion-based image encryption techniques, such as Fourier Transform (FT), Discrete Cosine Transform (DCT), and Discrete Wavelet Transform (DWT), in the transform domain. However, since these transform domain-based encryption algorithms usually use fixed basis functions (trigonometric functions, wavelet functions) in the process of transforming images, transform domain-based image encryption algorithms also have the risk of low security and easy to be cracked.

In order to design an image encryption method with strong security, it is difficult to further improve the security and reliability of the algorithm by encrypting images based on traditional transform domains (such as discrete FT transform, DCT transform, DWT transform, etc.).

SUMMARY OF THE INVENTION

In order to overcome the deficiencies of the prior art, the present invention provides a plaintext related image encryption method based on PUD adaptive decomposition, the method has strong robustness to noise attack, clipping and differential attack, and can be applied to image encryption protection. , the field of image security communication.

The present invention is achieved through the following technical solutions: the present invention provides a clear text related image encryption method based on PUD adaptive decomposition, comprising steps:

Step 1) take the original plaintext image to be encrypted, set the number of times of decomposition as N, and utilize a pseudo-random number generator to generate a pseudo-random sequence;

Step 2) Perform PUD adaptive decomposition on the original plaintext image:

The original plaintext image is decomposed according to the PUD decomposition technology, and three components are obtained, which are a two-dimensional component, two one-dimensional components and the grayscale average value of the original plaintext image;

Step 3) Image encryption operation:

The two-dimensional components obtained by decomposing the original plaintext image are encrypted by scrambling-diffusion method.

Wherein, in step 1) in the step of generating a pseudo-random sequence by using a pseudo-random number generator, a pseudo-random number sequence with a size of 256 bits is generated by using a pseudo-random number generator.

Wherein, step 1) includes the step of interpolating the original plaintext image after obtaining the original plaintext image to be encrypted, so as to convert the original plaintext image into a format with a pixel value format of M*M.

Wherein, in step 2), the PUD adaptive decomposition is performed on the original plaintext image, and after two one-dimensional components are obtained, the following steps are included:

Randomize the two one-dimensional components F ₁ , G ₁ , and perform an exclusive OR operation with the pseudo-random sequence generated by the pseudo-random number generator to obtain new one-dimensional components F ₂ , G ₂ .

Wherein, step 3) specifically includes the following steps:

Step 3a) use scrambling algorithm to perform global scrambling on the pixel value of the two-dimensional component, and change the similarity relationship of adjacent pixels;

Step 3b) adopts a diffusion algorithm to change the pixel value of the scrambled two-dimensional component, so that the encrypted pixel value is different from the original two-dimensional component pixel value, so as to ensure the security of the image.

Among them, the scrambling algorithm is Arnold transform.

Among them, the diffusion algorithm adopts the way of XOR operation.

Among them, the encryption algorithm corresponds to the decryption algorithm, and in the image decryption algorithm, the reverse operation is performed to correctly restore the decrypted image.

Compared with the prior art, the present invention has the following beneficial effects:

The invention proposes a plaintext related image encryption algorithm based on PUD adaptive decomposition; due to the adaptive property of the PUD decomposition method, for different images, the obtained one-dimensional components are completely different. Even for the same image, different one-dimensional components can be obtained after image decomposition by setting different times of decomposition. Thus, the image can be encrypted with a sequence associated with the plaintext. This technology can effectively resist chosen plaintext attack and chosen ciphertext attack. It has strong robustness to noise attack, clipping attack and differential attack, and has high security and robustness of image confidentiality, and can be applied to high-level image security and image confidentiality communication fields.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, in which:

FIG. 1 is a schematic flowchart of a plaintext related image encryption algorithm based on PUD adaptive decomposition provided by the present invention.

FIG. 2 is an original diagram of a plaintext related image encryption algorithm processing based on PUD adaptive decomposition provided by the present invention.

FIG. 3 is an image after encrypting the original image in a plaintext related image encryption algorithm based on PUD adaptive decomposition provided by the present invention.

FIG. 4 is a histogram effect diagram of the original image of FIG. 2 based on a PUD adaptive decomposition-based plaintext related image encryption algorithm provided by the present invention.

FIG. 5 is a histogram effect diagram of the encrypted image in FIG. 3 in a plaintext related image encryption algorithm based on PUD adaptive decomposition provided by the present invention

FIG. 6 is a decrypted image after adding Gaussian noise to the encrypted image by a plaintext related image encryption algorithm based on PUD adaptive decomposition provided by the present invention.

FIG. 7 is a decrypted image after adding salt and pepper noise to the encrypted image by a plaintext related image encryption algorithm based on PUD adaptive decomposition provided by the present invention.

FIG. 8 is a schematic diagram of a cropped region of an encrypted image in a plaintext related image encryption algorithm based on PUD adaptive decomposition provided by the present invention.

FIG. 9 is a schematic diagram of a plaintext related image encryption algorithm based on PUD adaptive decomposition provided by the present invention after cropping according to the area of FIG. 8 .

FIG. 10 is an image of the original plaintext image (FIG. 2) changed by a random bit in a plaintext related image encryption algorithm based on PUD adaptive decomposition provided by the present invention.

FIG. 11 is a ciphertext image of an original plaintext image in a plaintext related image encryption algorithm based on PUD adaptive decomposition provided by the present invention.

FIG. 12 is a ciphertext image after changing the image of a plaintext related image encryption algorithm based on PUD adaptive decomposition provided by the present invention.

FIG. 13 is the absolute difference between two ciphertext images of a plaintext related image encryption algorithm based on PUD adaptive decomposition provided by the present invention.

Detailed ways

In order to have a clearer understanding of the technical features, objects and effects of the present invention, the specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

As shown in FIG. 1 , the method for encrypting plaintext related images based on PUD adaptive decomposition described in this embodiment includes the following steps:

Step 1) Generation of pseudo-random number sequence:

Use the existing random number generator to generate a pseudo-random number sequence with a size of 512 bits;

Step 2) Decomposition of the plaintext image:

The original plaintext image is decomposed by PUD decomposition technology, and three components are obtained, which are a two-dimensional component, two one-dimensional components and the average gray level of the image;

Step 3) Operation of image encryption:

Aiming at the two-dimensional components obtained by decomposing the original plaintext image by PUD technology, scrambling-diffusion operation is performed, and finally an encrypted image is obtained.

Preferably, the step 2) specifically includes the following steps:

Step 2a) Perform PUD decomposition on the original plaintext image to obtain three-part components, including one two-dimensional component, two one-dimensional components and the grayscale average value of the original image.

In step 2b), the average value of the gray level of the image is processed by modulo operation to obtain two parameters of the generalized Arnold transform.

Step 2c) XOR the two one-dimensional components with the pseudo-random number sequence generated in step 1) to obtain two random sequences.

Preferably, the step 3) specifically includes the following steps:

Step 3a) scrambling operation is performed for the spatial pixels of the two-dimensional component to obtain a scrambling image; preferably, the scrambling algorithm adopted is Arnold transformation;

Step 3b) For the scrambled image, use two randomized one-bit sequences to perform the row and column XOR operation respectively, and diffuse the image to obtain an encrypted image.

Preferably, in the image encryption method related to plaintext, the number of times of decomposition needs to be set during the image encryption process. For the same image, different times of decomposition can be set to generate completely different keys and further generate completely different encrypted images. .

Specifically, step 1) specifically includes the generation of a pseudo-random number sequence, and a pseudo-random number sequence K with a length of 512 bits is generated by using a pseudo-random number generator.

In step 2), the PUD decomposition algorithm of the image is specifically included, and the steps are as follows:

Step 2.1: Select the number of decomposition times, decompose the original plaintext image I, and obtain three components, which are the two-dimensional component P, the one-dimensional components F ₁ , G ₁ , and the grayscale average value C ₀₀ of the original image.

Step 2.2: Perform two modulo operations on the average value C ₀₀ of the image gray level obtained after decomposition to obtain the two parameters p, q of the generalized Arnold change;

p=mod(c ₀₀ ×10 ¹⁵ ,255)

q=mod(c ₀₀ ×10 ¹⁷ ,255)

Step 2.3: Perform XOR operation on the two one-dimensional components F ₁ , G ₁ obtained after decomposing the original image with the pseudo-random sequence K to obtain two random sequences F ₂ , G ₂ .

Described step 3) specifically includes image encryption algorithm, including steps as follows:

Step 3.1: Use the Arnold transform to perform the following scrambling transformation on the pixel positions in the two-dimensional component P to obtain the scrambled image P'.

Step 3.2: For the scrambled image P', use F ₂ and G ₂ respectively according to row XOR and column XOR, and finally obtain an encrypted image.

The Lena image shown in Figure 2 is selected as the original plaintext image, and the number of times of decomposition is selected as N=5.

Step 1: the generation of the pseudo-random number sequence K, this step realizes the generation of the encryption key.

This step uses a random number generator to generate a key K with a length of 256 bits:

K='9F7ED402FBF47A4F91F44824E7288A684849B3E8C5F495384 96A3A83131373A5A510F5FF5DEDC6CD838DB139FB31E11D982C51 48C7A53B8380CB49AD6ADAC4D7' (hexadecimal form).

Step 2: PUD decomposition of the original plaintext image:

Described step 2 specifically includes the PUD decomposition of the image, including the steps as follows:

Step 1: Decompose the input plaintext image N times to obtain the two-dimensional component P, the one-dimensional components F ₁ , G ₁ , and the grayscale average value C ₀₀ of the original image.

I=P+F ₁ +G ₁ +C ₀₀

Taking the experiment as an example, the Lena image of size 256×256 is decomposed 5 times, and the two-dimensional component of size 256×256, two one-dimensional components F ₁ , G ₁ of 256 length, and the average gray level of the plaintext image will be obtained. value C ₀₀ .

Step 2: Perform the modulo operation on the average value of the image gray level C ₀₀ to obtain two parameters for the image scrambling stage, as shown below:

p=mod(C ₀₀ ×10 ¹⁵ ,255)

q=mod(C ₀₀ ×10 ¹⁷ ,255)

Step 3: Perform XOR operation on the two components F ₁ , G ₁ and the key K to obtain two random sequences F ₂ , G ₂ , as shown below:

Step 3: Encrypt the two-dimensional component, and the step 3 specifically includes an extraction algorithm for authentication information, including the following steps:

Step 1: The pixel position in the two-dimensional component P is scrambled in the following manner by using Arnold transformation to obtain the scrambled image P'.

Step 2: For the scrambled image P', use F ₂ , G ₂ respectively according to the row XOR and the column XOR, the specific process is as follows:

The XOR operation is performed sequentially from line 1 to line M:

i=1:M;

temp = P'(i,:);

P'(i,:)=P'(i,:)bitxor F ₂

The XOR operation is performed sequentially from column 1 to column M:

j=1:M;

temp=P'(:,j);

P'(:,j)＝P'(:,j)bitxor G ₂

Finally, the ciphertext image C is obtained.

As shown in Figure 2-3, Figure 2 is the original image and Figure 3 is the encrypted image.

Combined with Figure 4-5, Figure 4 is the histogram of the original plaintext image of Lena. It can be seen that the distribution of pixel values fluctuates greatly, and the histogram of the encrypted ciphertext image is shown in Figure 5. The distribution frequency is uniform, and the histogram is flat. It can be seen that the encryption method described in this embodiment can better resist statistical attacks, and the encryption effect is better.

Figures 6 and 7 show the decryption effect obtained by adding Gaussian noise and salt and pepper noise to the ciphertext image. Figure 6 is the decrypted image after adding Gaussian noise, and Figure 7 is the decrypted image after adding salt and pepper noise. It can be seen that this embodiment The encryption method described is resistant to noise attacks.

Figures 8 and 9 show the decryption effect after cutting the ciphertext image, Figure 8 shows the cropping area of the ciphertext image, Figure 9 shows the decrypted image after cutting, and it can be seen that the encryption method described in this embodiment Can cut attack.

When choosing a plaintext attack, the attacker will select an image to encrypt, and then randomly change the pixel value of the original image by 1 bit, encrypt the changed image, and then compare the differences between the two encrypted images in order to find the encrypted image. key clue. If a pixel value is randomly selected from the Lena image and its total one bit is changed, the encrypted image obtained from the original image and the changed image is completely different. As shown in Figure 10-13, Figure 10 is the original Lena image changed by a random bit, Figure 11 is the ciphertext image of the original Lena image, Figure 12 is the ciphertext image of the changed image, and Figure 13 is two ciphertext images The absolute value difference of the image. As can be seen from Figure 13, by randomly changing a random bit of the original plaintext image, the obtained ciphertext image is very different from the ciphertext image of the original image, so the method described in this embodiment can effectively resist differential attacks.

It can be seen that the present invention has strong robustness to these several image attack operations.

The embodiments of the present invention have been described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific embodiments, which are merely illustrative rather than restrictive. Under the inspiration of the present invention, without departing from the scope of protection of the present invention and the claims, many forms can be made, which all belong to the protection of the present invention.

Claims (4)

1. A plaintext related image encryption method based on PUD adaptive decomposition, is characterized in that, described method comprises the steps: Step 1) Take the original plaintext image to be encrypted, set the number of decompositions to N, and use the pseudo-random number generator to generate a pseudo-random sequence; in the step of using the pseudo-random number generator to generate the pseudo-random sequence, use the pseudo-random number generator to generate 256 A bit-sized pseudo-random number sequence; after obtaining the original plaintext image to be encrypted, the step of interpolating the original plaintext image is included, so as to convert the original plaintext image into a format whose pixel value format is M*M; Step 2) Perform PUD adaptive decomposition on the original plaintext image: Perform PUD adaptive decomposition on the original plaintext image to obtain two one-dimensional components, including steps: Randomize the two one-dimensional components F ₁ , G ₁ , and perform an exclusive OR operation with the pseudo-random sequence generated by the pseudo-random number generator to obtain new one-dimensional components F ₂ , G ₂ ; The original plaintext image is decomposed according to the PUD decomposition technology, and three components are obtained, which are a two-dimensional component, two one-dimensional components and the grayscale average value of the original plaintext image; Step 3) Image encryption operation: The two-dimensional components obtained by decomposing the original plaintext image are encrypted by scrambling-diffusion method. Specifically include the following steps: Step 3a) use a scrambling algorithm to globally scram the pixel values of the two-dimensional components to change the similarity relationship between adjacent pixels; Step 3b) adopts a diffusion algorithm to change the pixel value of the scrambled two-dimensional component, so that the encrypted pixel value is different from the original two-dimensional component pixel value, so as to ensure the security of the image. 2 . The plaintext related image encryption method based on PUD adaptive decomposition according to claim 1 , wherein the scrambling algorithm is Arnold transform. 3 . 3 . The plaintext related image encryption method based on PUD adaptive decomposition according to claim 1 , wherein the diffusion algorithm adopts an exclusive OR operation. 4 . 4. The plaintext-related image encryption method based on PUD adaptive decomposition according to claim 1, wherein the encryption algorithm corresponds to the decryption algorithm, and in the image decryption algorithm, the reverse operation is performed to correctly restore the decrypted image.

Images